Silica has been introduced as a filler in tire rubber compounding to provide improved traction, chunk and tear resistance of the rubber and to lower the rolling resistance. Silica particles have a strong tendency to aggregate due to the surface silanol (Si—OH) groups hydrogen bonding with one another causing difficulty in dispersion throughout the non-polar rubber matrix. Filler dispersion and reduction of filler-filler networking is an important aspect of rubber compounding. Desired targets on tear and rolling resistance are two properties affected by filler dispersion. To improve the filler dispersion in the rubber matrix, coupling agents have been introduced into rubber compounding. Coupling agents bridge the gap through physical or chemical bonding to improve filler dispersion between the non-polar rubber matrix and the polar filler surface. The most popular small-molecule bifunctional organosilane coupling agent used in rubber compounding with silica is bis(triethoxysilylpropyl)tetrasulfane) (TESPT or Si69). It contains triethoxysilane functional groups, which react and covalently bond with the Si—OH groups on the silica particle surface to improve the silica dispersion. The tetrasulfane linkage of TESPT undergoes crosslinking with the rubber chains during the curing of the rubber compound.
A typical tire tread rubber compound formulation incorporating silica as a filler does not solely rely on silica as the reinforcing filler; a hybrid filler system with carbon black and silica is common. Therefore, a coupling agent with the ability to interact with both carbon black and silica fillers is necessary. Poly(butadiene-graft-pentafluorostyrene) (PB-g-PPFS) has been studied as a coupling agent for both lignin and lignin-carbon black hybrid filler utilizing arene-perfluoroarene interactions between electron-deficient pentafluorostyrene and electron-rich lignin and carbon black π-systems. However, its interactions in a tire tread rubber compound formulation incorporating silica are limited. Therefore, there is a need in the art for coupling agents with the ability to couple fillers that include both carbon black and silica.